The instant invention relates to air seals, and specifically to air seals for rotary log debarking machines.
Log debarking machines are used in the forest product industry to remove bark from logs prior to the logs being further processed. A the typical log debarking machine includes a frame which has an air-tool-carrying ring rotatably mounted thereon. The tools are operable to scrape the bark off of the log as the log is carried along a log-transport axis through the machine. Such an operation produces a great deal of debris from the removed bark. The internal workings of the debarking machine must be protected from the debris. Additionally, means must be provided for providing an air supply to the tools located on the rotating ring. This is usually accomplished by means of a rotating air plenum which is carried on the ring and a stationary air plenum which is carried on a frame. The two air plenums are in contact with each other and provide the necessary means for conducting an air supply from the frame to the tools mounted on the ring. One such seal is disclosed in my prior issued U.S. Pat. No. 4,402,353, LOG DEBARKER WITH AIR SEAL COOLING FINS.
The conventional log debarking machine is arranged such that the frame provides an external, stationary mount with the ring rotating internally of the frame, and the log-transport axis extending through the ring. This configuration results in debris accumulating in the interior of the ring, where it is held by centrifugal force. Eventually, the debris builds up and may interfere with free passage of a log through the machine, or, the debris may work its way into the internal mechanism of the machine.
The normal arrangement of the air seal in log debarking machines includes a U-shaped channel having a seal-bearing face on either interior side thereof, and an annular ring disposed in the channel, having grooves disposed on either side thereof, with the air seal carried in the groove. Because the U-shaped channel is generally formed of two separate pieces, which allow the removal of one side of the channel during machine assembly and disassembly, the bearing face of the channel may flex, particularly as heat builds up in the system, resulting in an incomplete seal and loss of efficiency of transport of air between the stationary and rotary portions of the machine.
In the usual debarking machine, the air seal is maintained in contact with the moving bearing surface by means of a pre-compressed O-ring which is carried in the groove with the air seal. After a period of time, the O-ring looses resiliently and is unable to force the seal against the bearing surface. Simultaneously, the seal wears and is unable to maintain an air-tight condition. The net result is a loss of air pressure to the tools carried on the rotating portion of the machine.
The debarking machine of the instant invention includes a frame having a stationary central hub, and a ring rotatably mounted on the frame for rotation about the hub having air-pressure-actuated tools carried on the ring. Power means are provided for rotating the ring. Air passage means extend from the central hub to the ring for supplying actuating air to the tools. Air passage means includes a rotary-air-seal coupling, which comprises a substantially U-shaped channel formed of a pair of opposed L-shaped annular structures which extend about the hub and have a first air plenum carried therein. A pair of annular, floating seals are disposed on the interior side walls of the U-shaped channel and a rotary disc, having a second air plenum therein, is mounted on the ring and received in the U-shaped channel, in rotatable contact with the air seals.
An object of the instant invention is to provide a log debarking machine having a non-rotating central hub.
Another object of the instant invention is to provide a log debarking machine which includes an air passage means therein which provides for easy removal and replacement of a tool carrying ring of the machine.
A further object of the instant invention is to provide a log debarking machine having a rotary-air-seal coupling wherein a wear surface is carried on a single member thereof.
Yet another object of the instant invention is to provide a debarking machine having a rotary-air-seal coupling wherein the air seals are urged against a bearing surface by means of air pressure in the coupling.
These and other objects of the instant invention will become more fully apparent as the description which follows is read in conjunction with the drawings.